The present invention relates generally to diagnostic imaging and, more particularly, to a docking station that regulates the temperature of a stored detector.
X-ray imaging is a non-invasive technique to capture images of medical patients for clinical diagnosis as well as inspect the contents of sealed containers, such as luggage, packages, and other parcels. To capture these images, an x-ray source irradiates a scan subject with a fan beam of x-rays. The x-rays are then attenuated as they pass through the scan subject. The degree of attenuation varies across the scan subject as a result of variances in the internal composition of the subject. The attenuated energy impinges upon an x-ray detector designed to convert the attenuating energy to a form usable in image reconstruction. A control system reads out electrical charge stored in the x-ray detector and generates a corresponding image. For a conventional, screen film detector, the image is developed on a film and displayed using a backlight.
Increasingly, flat panel, digital x-ray detectors are being used to acquire data for image reconstruction. Flat panel detectors are generally constructed as having a scintillator, which is used to convert x-rays to visible light that can be detected by a photosensitive layer. The photosensitive layer includes an array of photosensitive or detection elements that each store electrical charge in proportion to the light that is individually detected. Generally, each detection element has a light sensitive region and a region comprised of electronics to control the storage and output of electrical charge. The light sensitive region is typically composed of a photoconductor, and electrons are released in the photoconductor when exposed to visible light. During this exposure, charge is collected in each detector element and is stored in a capacitor situated in the electronics region. After exposure, the charge in each detector element is read out using logic controlled electronics.
Each detector element is conventionally controlled using a transistor-based switch. In this regard, the source of the transistor is connected to the capacitor, the drain of the transistor is connected to a readout line, and the gate of the transistor is connected to a scan control interface disposed on the electronics in the detector. When negative voltage is applied to the gate, the switch is driven to an OFF state, i.e. no conduction between the source and drain. On the other hand, when a positive voltage is applied to the gate, the switch is turned ON resulting in connection of the source to the drain. Each detector element of the detector array is constructed with a respective transistor and is controlled in a manner consistent with that described below.
Specifically, during exposure to x-rays, negative voltage is applied to all gate lines resulting in all the transistor switches being driven to or placed in an OFF state. As a result, any charge accumulated during exposure is stored in each detector element capacitor. During read out, positive voltage is sequentially applied to each gate line, one gate at a time. In this regard, only one detector element is read out at a time. A multiplexer may also be used to support read out of the detector elements in a raster fashion. An advantage of sequentially reading out each detector element individually is that the charge from one detector element does not pass through any other detector elements. The output of each detector element is then input to a digitizer that digitizes the acquired signals for subsequent image reconstruction on a per pixel basis. Each pixel of the reconstructed image corresponds to a single detector element of the detector array.
As described above, indirect detection, digital x-ray detectors utilize a layer of scintillating material, such as Cesium iodide (Csl), to convert incident radiation to visible light that is detected by light sensitive regions of individual detector elements of a detector array. Generally, the transistor controlled detector elements are supported on a thin substrate of glass. The substrate, which supports the detector elements as well as the scintillator layer, is supported by a panel support. The panel support is not only designed to support the detector components, but also isolates the electronics that control the detector from the image detecting components. The electronics are supported by the panel support and enclosed by the back cover.
As described above, x-ray detectors have a multitude of electronic components. These electronic components are increasingly requiring more power to carry out the complex processes required for operation of the x-ray detector, e.g. data acquisition and data readout. These increased power requirements can expose the x-ray detector to increased thermal loads thereby resulting in “hot spots” on an external surface of the x-ray detector. As such, when a hot spot occurs, the x-ray detector must be removed from service and allowed to cool.
One proposed solution is to incorporate a fan in the x-ray detector that is designed to exhaust heated air to a cooler ambient. While such a solution may work in principle, as a medical device, an x-ray detector must remain sealed such that disinfectant and other sterilizing products can be applied without damaging the internal detector components. As such, designing the x-ray detector to have an exhaust port that would allow the ingress of cleaning agents is not practicable. Additionally, such an exhaust port would allow the ingress of dust and other fine particle debris that may interfere with operation of the x-ray detector.
Other proposed solutions include radiation and free convection; however, both are inadequate in responsively regulating the temperature of an x-ray detector. Since an x-ray detector has relatively little surface area, radiation losses are low and not rapid. Similarly, free convection does not remove a sufficient amount of heat to maintain the x-ray detector at a required temperature in a responsive manner. That is, x-ray detectors are iteratively placed in an in-use state and a non-use state. If a hot spot develops while the x-ray detector is in-use, the x-ray detector must be removed from use and allowed to cool. Free convection is capable of removing the heat but the time required to do so can be lengthy, resulting in considerable down-time of the x-ray detector. This can be problematic for high use facilities such as emergency rooms, triage centers, and the like where turnaround time can be critical to diagnosing a patient. The same criticality can be found in non-medical environments such as baggage screening at airports, postage facilities, etc.
Also, these proposed solutions are solely concerned with dissipating heat from an x-ray detector, not maintaining the temperature of the x-ray detector within a prescribed temperature range. It is well-recognized that the components of an x-ray detector operate more efficiently when the temperature of the components are maintained within a given range. Accordingly, there is a need to dynamically monitor the temperature of an x-ray detector when not in use and actively regulate the temperature of the detector to be within a given range. As such, when the x-ray detector is placed in use after a period of non-use, the time customarily required to heat-up to an optimal temperature is avoided thereby further reducing the down-time of the x-ray detector.
Therefore, it would be desirable to design an apparatus that stores an x-ray detector during x-ray detector non-use and regulates the temperature of a stored x-ray detector to enhance operability of the x-ray detector when the x-ray detector is removed from storage and placed in use.